This invention relates to an image formation method by chromogenic reaction in a light and pressure sensitive sheet comprised of a light-accepting sheet and an image transfer sheet, and more particularly to a method and apparatus for improved protection of microcapsules with which a surface of the light-accepting sheet is coated such that these microcapsules are not easily damaged.
Japanese Patent Publications Tokkai 58-88739 and 59-149343 have disclosed light and pressure sensitive image formation materials comprised of a light-accepting sheet with a base sheet coated with microcapsules encapsulating a colorless dye and a photopolymerizing agent and an image transfer sheet coated with a developing agent for chromogenic reaction of this colorless dye. As shown in FIG. 1, a prior art copier using such an image formation material is so structured that the microcapsule-coated surface of a light-accepting sheet 51 is exposed to light reflected from an original image to be copied to form thereon an invisible (latent) hardened image by selectively hardening those of the microcapsules exposed to light energy by the polymerization of the encapsulated photopolymerizing agent. An image transfer sheet 52, originally kept in the form of a roll, is thereafter superposed such that the hardened image formed on the light-accepting sheet 51 and the surface of the image transfer sheet 52 coated with the developing agent are directly in contact in face-to-face relationship with each other. As they are thereafter passed and pressed together between pressure applying rollers 53a and 53b, those of the microcapsules which were not hardened when the light-accepting sheet was exposed to light rupture, allowing the colorless dye, etc. encapsulated inside to flow out to react with the developing agent on the image transfer sheet 52 and forming a visible image thereon. After the formation of a visible image on the image transfer sheet 52, the light-accepting sheet is separated therefrom and the image transfer sheet 52 with a visible image thereon is discharged onto a discharge tray 55 by means of discharge rollers 54. Alternatively, this technology described above may be applied to a printer.
According to the technology described above including the step of superposing a light-accepting sheet and an image transfer sheet after the light-accepting sheet is exposed to light, however, the light-accepting sheet remains unprotected for a long period of time until the aforementioned superposition step is effected. Thus, the microcapsules on the surface of the light-accepting sheet are easily damaged and/or ruptured. In order to prevent such damage to the microcapsules, a complicated transportation system including a suction device 56 or the like is commonly provided to properly position the light-accepting sheet such that no external force is applied on its coated surface.